Method of balancing tires



May 20, 1941. I m. KRAFT 2,242,430

METHOD OF BALANCING TIR-ES Filed Sept. 7, 1939 INVENTOR Herman, T. KraftATTORNEYS Patented ay '20, 194i UNITED STATES' PATENT OFFICE LIETHOD OFBALANCING TIRES Herman '1. Kraft, Akron, Ohio, assignor to The GeneralTire & Rubber Company, Akron, Ohio, a corporation of Ohio ApplicationSeptember 7, 1939, Serial No. 293,771

3 Claims.

This invention relates to rubber tires and to a method of balancing sucha tire by which a substantially uniform distribution of weight about theaxis of the tire is obtained.

Fig. 4 is a view showing one of the metal slugs on an enlarged scale;

Fig. 5 is a fragmentary-sectional view showing the manner of insertingthe slugs in the holes In the manufacture of pneumatic tires it is 5previously formed by the perforating tool; found that most of the tiresare not perfectly Fig. 6 is a perspective view of the jig; uniform andthat some portions thereof are Fig. '7 is a perspective view of analternative somewhat heavier than others, with the result form ofperforating tool; and that when mounted upon a wheel and rotated Fig. 8is a perspective view showing another at high speeds, the centrifugalforce is not uni- 10 form of perforating tool. form throughout the tireperiphery and the In the accompanying drawing the invention is vehiclewheel is imperfectly balanced. Uniform shown applied to a pneumatic tireI which has distribution of weight in the wheel and tire is a fabriccarcass 2 and rubber tread 3 which has desirable for easy riding,economy of power and radially deep shoulder portions 4. The methoduniform wear on the tires. of the present invention consists inbalancing It has heretofore been proposed to balance a tire by insertingslugs of heavy metal into the rubber tired wheels by attaching weightsat body of rubber which forms the tread in portions selected points onthe tire supporting rim', but of the tire which are light as compared toother such weights are unsightly and do not fully portions of the tire,the points at which the slugs compensate for inequalities in the tirebecause are to be inserted being ascertained by suitable of the factthat they are placed at a considerbalance indicating devices well knownin the able distance from the tire periphery. art. After the portions ofthe tire which are The present invention has for its object to deficientin weight have been ascertained, weight balance a tire by the insertionof weights into is added to these portions by forming holes of selectedportions of the tire tread in such manner Small cro s Sect exte w y111170 a as to enclose the weights within the body of shoulder portionof the tire from the side face rubber forming the tire tread. thereof,after which a. slug of heavy metal of a The present invention has for afurther object cross sectional size greater than that of the hole toprovide a simple and inexpensive method of is forced into the holeto'the inner end thereof, inserting weights, for example, slugs of aheavy a suitable number of slugs being inserted in the metal such aslead or lead alloy, into shoulder selected portions of the tire tread tosubstanportions of the tire tread in such manner that tially balance thetire. the slugs are permanently secured in place en- In order to enablethe holes to be made in tirely within the rubber of the tread. the sidesof the tread shoulders without detract- With the above and other objectsin view, the ing from the appearance of the tire, a series of inventionmay be said to comprise the balanced regularly spaced indentations ofcircular or other tire and method of balancing the same as illusfo m,such as ind d y h eral 5 in trated in the accompanying drawinghereinafter Fig. 1, may be molded on the side faces of the described andparticularly set forth in the aptire shoulders. By forming the holes inthe pended claims, together with such variations selected portions ofthe tire at the depressions, and modifications thereof as will beapparent the holes will not be noticeable. to one skilled in the art towhich the invention As shown in Fig. 2 of the drawing, holes 6 ofappertains. Reference should be had to the small 0!0SS S8CtlOl1 areformed in the shoulder accompanying drawing forming part of thisportions 4 of the tire. These holes extend inspecification, in which:'wardly into the shouldenfrom a point spaced Figure 1 is a fragmentaryside elevation showinwardly from the tread surface. After the hole ing atire with a jig and perforating tool in place 6 is formed, a metal slug1, which is preferably thereon; of substantially spherical form and of adiameter Fig. 2 is a fragmentary section on an enlarged considerablygreater than that of the hole 6, is scale through a tread shouldershowing a metal forced into the hole to the inner end thereof. slug inplace therein; The rubber surrounding the slug 1 is put under Fig. 3 istransverse section through the tire compression and firmly holds theslug in place showing a jig placed on the tire and a perforatwithin thetire tread. ing tool inserted to full depth into the tread As best shownin Fig. 3, a perforating tool 8 shoulder; is provided which has a handle9 to which is attached a rod I of small diameter. The rod I0 is adaptedto be heated electrically, the tool being provided with a sleeve llenclosing the inner end of the rod III in which suitable resistanceheating elements may be placed. Current for heating the rod is suppliedthrough a suitable extension cord [2.

In order to properly position the perforating tool and to accuratelygauge the depth of the holes formed by the tool, a suitable jig I3 isprovided, the body portion which is formed to fit against a side face ofthe tire. The jig l3 has a flange M which engages upon the peripheralsurface of the .tread and a handle l5 by means of which the jig may beheld in position on the tire. The jig is provided with a boss l5 whichhas a central hole I! in which the rod ID has a sliding fit. In formingthe holes in the tire shoulders the jig I3 is placed upon the tire andthe rod I0 is inserted into the hole I! of the jig and pushed inwardly.until the end ofthe sleeve ll engages the boss l6, whereupon the rod IIIis immediately withdrawn. The heated rod readily enters the rubber ofthe tire shoulder and when withdrawn leaves an opening in the rubberwhich is of a diameter considerably less than the rod. After a hole 6 isformed in the indentations 5 in the tire shoulder so that after the holeis formed it will require close inspection to see the hole because ofthe general similarity of the hole to the regularly spaced indentationsalready formed in the tire.

As shown in Figs. 2 and 3 of the drawing; the holes 6 are so formed thatthey are entirely within the rubber of the tire shoulder outwardly tireshoulder, one of the metal slugs 1 is inserted into the hole by means ofa suitable tool [8 which has a handle l9 and a rod 20 attached theretowhich is provided with a concave end 2|. The

slug I is placed at the outer end of the opening and is engaged by theconcave end 2| of the rod 20, which is then pushed into the hole 6 bymeans of the handle I.

In order to prevent trapping of air in the hole 6 between the inner endof the hole and slug 1, and in order to more securely hold the slug inplace after it is inserted in the hole, the slug, as shown in Fig. 4, ispreferably provided with a surface which has been roughened in anysuitable way, as, for example, by knurling.

The perforating rod may be round in cross section, as shown in Fig. 3,or it may have other shapes in cross section.. The perforating tool 22shown in Fig. 7 is provided with a flat rod 23,

and the perforating tool 24 shown in Fig. 8 is provided with a rod 25which is triangular in cross section. The flat or triangular rods havethe advantage that there is somewhat less tendency to trap air behindthe slug when it is inserted into the hole. 1

In forming the hole 6 the jig I3 is placed with its hole I! directlyover one 01' the molded of the tire carcass but within the grooves ordepressions of the tire tread. 'The holes 6 preferably are inclinedoutwardly toward the tread periphery so as to position the holes at adistance from the tread surface such that rubber in which the holes-arelocated will remain after the tread ribs or blocks have worn away.

The present invention provides a verysimple and economical method ofbalancing tires which is highly effective because of the fact that theweight is added to the tire adjacent the periphery thereof and in suchmanner that the added weight may be distributed advantageously overconsiderable portions of the tire periphery.

Furthermore, it is to be understood that the particular procedure setforth is presentedfor purposes of explanation and illustration and thatvarious modifications of said procedure can be made without departingfrom my invention as defined in the appended claims.

What I claim is;

1. The herein described method of balancing a rubber tire which consistsin forming in a selected portion of the tread periphery one or moreholes of small cross section extending laterally into the rubber of thetire tread, and forcing into said holes slugs of metal of a crosssectional size greater than the holes.

2. The herein described method of balancing a rubber tire which consistsin. forming in a selected portion-of the tread periphery one or moreholes of small cross section extending from a side face of a tireshoulder and at an outward inclination, and passing a metal slug of across sectional size greater than the hole into each hole to adjacentthe inner end thereof.

3. The herein described method of balancing a rubber tire which consistsinforming in a selected portion of the tread periphery one or more holesof small cross section extending laterally into the rubber of the tiretread by forcing a heated rod endwise into the tire tread andimmediately withdrawing the rod, and pushing a metal slug of a crosssectional size greater than the hole into each of the holes so formed.

HERMANT. KRAFT.

